Rails 5: Bootstrap not styled properly

Question

I am just starting to use bootstrap (I mostly work back-end) and I am a bit confused. I have configured it properly (followed every step of their guide for the bootstrap-gem setup) but when I copy the code for a navbar, from the examples at their site, it is not styled at all (other than positioning).

Please, tell me what code should I provide because I am really out of my league here.

Thank you

My application.js

//= require jquery3
//= require rails-ujs
//= require turbolinks
//= require popper
//= require bootstrap
//= require_tree .

This is added to my Gemfile

gem 'bootstrap', git: 'https://github.com/twbs/bootstrap-rubygem'
gem 'jquery-rails'
gem 'sprockets-rails'

in my application.html.erb

<nav class="navbar navbar-default navbar-fixed-top">
  <div class="container">
    <%= link_to 'Home', movies_path %>
    <% if user_signed_in? %>
        Logged in as <strong><%= current_user.email %></strong>.
        <%= link_to 'Edit profile', edit_user_registration_path, :class => 'navbar-link' %> |
        <%= link_to "Logout", destroy_user_session_path, method: :delete, :class => 'navbar-link' %>
    <% else %>
        <%= link_to "Sign up", new_user_registration_path, :class => 'navbar-link' %> |
        <%= link_to "Login", new_user_session_path, :class => 'navbar-link' %>
    <% end %>
  </div>
</nav>

and it's head is

<%= stylesheet_link_tag 'application', media: 'all', 'data-turbolinks-track': 'reload' %>
  <%= javascript_include_tag 'application', 'data-turbolinks-track': 'reload' %>

Finally in my application.scss

@import "bootstrap";

Answer 1

This is actually a bootstrap problem, I asked on GitHub and others are facing the same problem.